1854 results about "Carbon coating" patented technology

The invention provides a preparation method of a porous carbon-silicon composite negative electrode material of a lithium battery. The preparation method comprises the following steps: constructing a multi-stage template system; carrying out carbon precursor impregnation and gradient temperature carbonization on the multistage template system; removing the template to form a gradient porous carbon carrier; carrying out gradient temperature zone silane deposition; and plasma-assisted carbon coating and nitrogen doping are carried out. According to the method, a silicon dioxide sphere hard template is combined with cetyltrimethylammonium bromide and a block copolymer soft template to form a porous carbon carrier with a micropore-mesopore-macropore three-stage structure, and gradient distribution of silicon in porous carbon is realized by utilizing a three-temperature-zone fluidized bed reactor and a pulse type deposition technology, so that the silicon-based porous carbon composite material is obtained. The problem of volume expansion of the silicon material is effectively relieved and the material cycling stability is improved. The porous carbon-silicon composite negative electrode material prepared by the invention has high specific surface area, excellent ion transmission channel and good structural stability, and can be applied to a high-energy-density lithium ion battery.

The invention relates to a silicon-carbon composite material and a preparation method and application thereof.The preparation method comprises the steps that a porous graphite raw material is subjected to acid pickling and smashing to obtain pretreated porous graphite, then the pretreated porous graphite is soaked in a carbon precursor solution in a vacuum mode, carbonization treatment is conducted after centrifugal separation, pores of the porous graphite are filled with carbides, physical activation is conducted, and the silicon-carbon composite material is obtained; the preparation method comprises the following steps: forming pores in a carbide to form a graded pore structure to obtain a porous graphite composite material, then carrying out silicon deposition in a fluidized bed to obtain a uniform nano silicon layer, and then carrying out carbon coating treatment to obtain a silicon-carbon composite material; the graphite with relatively low cost is adopted as a matrix, high capacity and long cycle performance of the graphite-based silicon-carbon negative electrode material are realized through hierarchical pore structure design, carbonization-activation synergistic pore forming and interface deposition process optimization, and the graphite-based silicon-carbon negative electrode material can be applied to the fields of power batteries and high-energy-density energy storage, especially the field of lithium ion batteries and has wide application prospects. The expansion rate of the battery can be reduced, and the specific capacity, cycling stability and safety of the lithium ion battery can be improved.

The invention relates to the technical field of electrode materials, in particular to a silicon-carbon negative electrode material and a preparation method and application thereof. The silicon-carbon negative electrode material comprises a plurality of silicon-carbon composite particles, each silicon-carbon composite particle comprises porous carbon, nano silicon particles and phosphorus element which are attached in pores of the porous carbon, and coating carbon for coating the porous carbon, and n-type doping of the phosphorus element is formed at the joint of the nano silicon particles and the porous carbon. The preparation method comprises the following steps: (1) adsorbing phosphoric acid in porous carbon, and carrying out a heating reaction in a protective gas atmosphere to generate phosphorus-infiltrated porous carbon; (2) introducing a gaseous silicon source in a protective gas atmosphere, and carrying out silicon deposition on the phosphorus-infiltrated porous carbon by adopting a chemical vapor deposition method to obtain a phosphorus-doped silicon carbon material; and (3) carrying out carbon coating on the phosphorus-doped silicon carbon material to obtain the phosphorus-doped silicon carbon material. According to the method, the rate capability of the silicon-carbon negative electrode material can be remarkably improved while high first efficiency and high gram capacity are ensured.

The invention relates to a silicon-carbon composite material capable of improving the cycling stability of a battery, a preparation method of the silicon-carbon composite material, a negative pole piece and a lithium ion battery. The carbon-silicon composite particle comprises a silicon-carbon inner core and a carbon coating layer, nano-silicon is attached in holes and / or on the surface of a porous carbon matrix to form the silicon-carbon inner core, and the carbon coating layer is coated on at least part of the surface of the inner core; the porous carbon matrix and the carbon coating layer are both doped with halogen. According to the silicon-carbon composite material, the electron conductivity of the silicon-carbon composite material is improved by doping the halogen in the porous carbon matrix inside the silicon-carbon composite material and the carbon coating layer outside the silicon-carbon composite material; and meanwhile, the porous carbon matrix, the inner core composed of the nano silicon and the carbon coating layer are mutually matched and have synergistic interaction, so that the volume expansibility and defects of the silicon-carbon composite material are reduced, and the cycle stability is improved.

The invention provides an in-situ modified lithium-rich manganese-based precursor and a preparation method and application thereof.The preparation method comprises the following steps that a nickel-cobalt-manganese mixed metal salt solution, a precipitator solution and a complexing agent solution are introduced into a base solution for a first coprecipitation reaction, and after the first coprecipitation reaction is finished, feeding is stopped; and introducing a doped nickel-cobalt-manganese mixed metal salt solution, a precipitant solution, a complexing agent solution and a carbon source solution into a system after the first coprecipitation reaction is finished, and carrying out a second coprecipitation reaction to obtain the in-situ modified lithium-rich manganese-based precursor. According to the preparation method, doping elements and a carbon source are introduced when the lithium-rich manganese-based precursor is prepared through the coprecipitation reaction, in-situ uniform construction of oxygen vacancies and a carbon coating layer on the surface of the material is synchronously achieved, the in-situ modified lithium-rich manganese-based precursor is obtained, the treatment step of subsequent secondary coating can be reduced, the production cost can be reduced, and the method is suitable for industrial production. The technological process is shortened.

The invention relates to a solid electrolyte coated silicon-carbon negative electrode material and a preparation method thereof, an all-solid-state battery and an electric device, and belongs to the technical field of methods or devices for directly converting chemical energy into electric energy. The solid electrolyte coated silicon-carbon negative electrode material comprises a silicon-carbon negative electrode material and a solid electrolyte coating layer arranged on the surface of the silicon-carbon negative electrode material, the solid electrolyte coating layer comprises at least one of sulfide electrolyte and halide electrolyte; the silicon-carbon negative electrode material comprises an inner core and a carbon coating layer arranged on the surface of the inner core, the inner core comprises a porous carbon matrix and a silicon-based material positioned in pores of the porous carbon matrix. The solid-state electrolyte coated silicon-carbon negative electrode material enables an all-solid-state battery to have high ionic conductivity and first efficiency and excellent cycling stability.

The invention relates to the technical field of sole processing, in particular to a sole composite processing method, which comprises the following steps: according to the rigidity requirement of an arch support area, preparing high-density slurry in which silicon nitride ceramic powder accounts for 30-40%, forming # imgabs0 # crystal phase through microwave-assisted sintering, and controlling the porosity to be 10-20%; according to the energy rebound requirement of the forefoot buffer area, graphene oxide / carboxymethyl cellulose aerogel powder is added into the slurry until the concentration is 25%, and the porosity is increased to 40-60% by combining the honeycomb porous network design; a nano silicon dioxide reinforcing agent is introduced into a wear-resistant area of the heel to 15%, a diamond-like carbon coating is formed through plasma surface treatment, and the porosity is limited to be 5-15%. According to the invention, silane is encapsulated by adopting polyurea microcapsules, and is released only when the material is damaged, so that dynamic self-repairing is realized, the shoe sole is endowed with dynamic repairing capability, and the service life is prolonged.

The invention relates to the field of batteries, in particular to a preparation method and system of a silicon-carbon material, and the preparation method comprises the following steps: pretreating porous carbon, conveying the pretreated porous carbon to a fluidized bed reactor, sequentially introducing a silicon source gas and a carrier gas for silicon deposition treatment, heating, introducing a carbon source gas, adjusting the flow of the carrier gas for carbon coating treatment, and discharging and cooling to obtain a finished product, meanwhile, reaction tail gas is recycled. The preparation system comprises a gas inlet unit, a fluidized bed reactor unit, a tail gas circulation unit, a feeding preheating unit and a discharging unit. The fluidized bed reactor comprises an outer shell, an up-down stirring device, a heat exchange assembly and an air distribution assembly, and efficient reaction and temperature control can be achieved. The silicon-carbon material prepared by the method has excellent electrochemical performance and is suitable for a lithium ion battery negative electrode material. The unique porous structure and the uniform carbon coating layer effectively improve the conductivity and the structural stability of the material, and meanwhile, the volume expansion effect of silicon in the charging and discharging process is reduced.

The invention relates to a sodium ion battery, and belongs to sodium ion batteries. The battery cell of the sodium-ion battery comprises a positive plate, a negative plate and an electrolyte, the active material of the positive plate is carbon-coated aluminum-doped sodium ferric sulfate; the chemical formula of the aluminum-doped sodium ferric sulfate is Na < 2 + 2y > Fe < 2-x-y > Al < x > (SO4) 3, x is more than or equal to 0.01 and less than or equal to 0.05, and y is more than or equal to 0.1 and less than or equal to The particle size of the carbon-coated aluminum-doped sodium ferric sulfate ranges from 50 nm to 100 nm; the weight ratio of a carbon coating layer in the carbon-coated aluminum-doped sodium ferric sulfate is 1%-5%; the active material of the negative plate is carbon-coated sodium titanate; the specific surface area of the carbon-coated sodium titanate is 20 m < 2 > / g to 25 m < 2 > / g; the weight ratio of a carbon coating layer in the carbon-coated sodium titanate is 0.5%-3%. Volume expansion is jointly inhibited through structural stability of positive and negative electrode materials, and the cycle life is prolonged.

The invention relates to the technical field of batteries, in particular to a composite negative electrode material as well as a preparation method and application thereof. The composite negative electrode material comprises a negative electrode base material and a fast ion conductor layer located on the surface of the negative electrode base material, the negative electrode base material comprises a silicon nanosheet and a carbon coating layer located on the surface of the silicon nanosheet, and the surface of the carbon coating layer is doped with element nitrogen; and the fast ion conductor layer comprises Li3PO4. According to the composite negative electrode material disclosed by the invention, through coordination and cooperation of all the layers, the problem of capacity fading of a pure silicon negative electrode in a circulation process can be relieved, stable long-cycle performance is realized, and a high capacity retention ratio is obtained.

The application relates to the technical field of material preparation, and discloses multi-element carbon-coated lithium manganate, a preparation method thereof and a secondary battery. The multi-element carbon-coated lithium manganate comprises a lithium manganate core and a carbon nanotube layer and a hard carbon layer which are sequentially coated on the lithium manganate core. The chemical formula of the lithium manganate core is LiAl a X b Mn 2‑a‑b O4, wherein 0.01<=a<=0.10, 0.01<=b<=0.05, and X comprises at least one of Co, Cr, Ti, V and B. The preparation method of the multi-element carbon-coated lithium manganate comprises the following steps: (I) preparing doped lithium manganate, (II) preparing carbon nanotubes and (III) multi-element carbon coating. The multi-element carbon-coated lithium manganate has high conductivity, rate performance, cycle performance and safety performance, and can be used as an alternative positive electrode material with high cycle and excellent fast-charging performance.

The invention belongs to the technical field of batteries, and discloses a composite lithium supplement agent, a positive pole piece, a battery and electric equipment. The composite lithium supplement agent comprises an inner core and a shell covering the inner core, wherein the shell comprises a carbon coating layer; the carbon coating layer comprises a cage-shaped ball structure, and the carbon coating layer has elasticity; the inner core comprises a lithium supplementing material. The composite lithium supplement agent can adapt to the volume change of the lithium supplement material during the first lithium removal, and the contact between the electrolyte and the interior of the composite lithium supplement agent or a decomposition product is avoided, so that the side reaction of an interface is reduced, the gas production is reduced, the battery capacity is improved, and the stability and safety of the battery are favorably improved.

The invention discloses a method for preparing a platinum-based alloy catalyst by using a plasma enhanced chemical vapor deposition low-temperature technology, relates to a preparation method of a platinum-based alloy catalyst, and aims to solve the technical problems that a carbon layer is not uniformly coated and metal particles of the catalyst are easy to agglomerate in a high-temperature calcination process in the existing platinum-based alloy catalyst prepared by carbon coating. The method comprises the following steps: 1, preparing Pt / C by a polyhydric alcohol reduction method; 2, pre-treating a Pt / C catalyst; 3, preparing M-Pt / C by a dipping evaporation method; 4, PECVD carbon shell coating is carried out; (5) alloying; and 6, removing a part of carbon shell to obtain the platinum-based alloy catalyst. When the Pt / C catalyst is used for preparing a membrane electrode of a proton exchange membrane fuel cell, the peak power density can reach 1.72-1.89 W / cm < 2 > under a hydrogen-air condition, which is improved by 20.3% and 32.2% compared with a membrane electrode of a commercial 20% Pt / C catalyst, and the Pt / C catalyst can be used in the field of proton exchange membrane fuel cells.

The invention provides a Na / P double-site doped phosphoric acid ferric sodium pyrophosphate / carbon positive electrode active material and a preparation method and application of the Na / P double-site doped phosphoric acid ferric sodium pyrophosphate / carbon positive electrode active material. The material comprises a Na / P double-site doped ferric sodium pyrophosphate base material and a carbon coating layer coating the surface of the base material, the general formula of the base material is Na (4-x) MxFe3 (PO4) 2-y (QO4) y (P2O7), 0 lt, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 X is less than or equal to 0.4, 0lt; y < = 0.2; m is at least one of K, Li, Mg, Ca and Sr, and Q is at least one of Si, Ge, B and S; specific elements are introduced to the Na site and the P site to form a synergistic doping structure, so that the crystal structure and charge distribution are regulated and controlled, and the electrochemical performance of the material is further improved; the material disclosed by the invention is simple and convenient to prepare, wide in raw material source, suitable for electrochemical energy storage systems such as sodium ion batteries and the like, and excellent in rate capability and long in cycle life.

The invention belongs to the technical field of battery material preparation, and particularly relates to a coated negative electrode material as well as a preparation method and application thereof. The coated negative electrode material comprises a porous carbon skeleton and a carbon coating layer coating the porous carbon skeleton, the porous carbon skeleton is provided with a plurality of holes; a silicon layer and a functional layer are attached to the surfaces of part of the holes; the silicon layer comprises silicon, the functional layer comprises a functional material, and the functional material comprises lithium aluminum fluoride. The coated negative electrode material provided by the invention has the properties of low expansion, high lithium ion conduction, few byproducts and the like, and is suitable for a solid battery; the battery energy density is ensured, and the problems that an effective lithium ion path cannot be formed due to contact failure of an active substance caused by high volume expansion of a silicon-based material in the circulation process and contact failure of the active material and a solid electrolyte in a solid-state battery, and performance degradation is caused by negative electrode side polarization increase in the circulation process are solved.

The invention relates to the technical field of lithium ion batteries, in particular to a carbon source mixed gas CVD coated silicon-carbon negative electrode material, a preparation method and a lithium ion battery. The preparation method comprises the following steps: 1) preparation of a silicon-carbon material: placing porous carbon in equipment, regulating and controlling the gas speed and the dynamic rotation speed of the equipment to uniformly disperse the porous carbon, heating to 380-650 DEG C, and introducing silane mixed gas with the concentration of 5-50% to form the silicon-carbon material; and 2) coating the silicon-carbon material with mixed gas carbon: introducing mixed gas sources with different proportions into equipment, regulating and controlling the gas speed and the dynamic rotation speed of the equipment to uniformly disperse the mixed gas sources, and heating to 450-700 DEG C to realize uniform carbon coating on the surface of the silicon-carbon material. According to the invention, the problem of explosion caused by self-polymerization reaction of single acetylene is solved; and moreover, the uniform carbon coating isolates the side reaction problem caused by direct contact between the electrolyte and the nano silicon, and the stability of the silicon-carbon material is improved.

The invention provides a phenolic resin-based spherical silicon-carbon composite material as well as a preparation method and application thereof, and belongs to the technical field of lithium battery materials. The preparation method comprises the following steps: preparing spherical phenolic resin by adopting a suspension polymerization method, curing to obtain phenolic resin microspheres, preparing porous carbon spheres by taking the phenolic resin microspheres as a carbon precursor in a carbonization and alkali activation manner, carrying out CVD vapor deposition on nano silicon, and carrying out carbon coating to obtain the phenolic resin-based spherical silicon-carbon composite material. The phenolic resin is utilized to form a highly cross-linked network structure after curing, the carbon spheres obtained after carbonization have good mechanical strength and rigidity, the porous structure of the porous carbon spheres provides a volume change buffering structure for nano-silicon, the lithium ion path is shortened, the spherical structure is beneficial to uniform dispersion, nano-silicon particles are prevented from gathering, and the performance of the lithium ion battery is improved. And the porous carbon spheres with high specific surface area can also improve the interface reaction activity, so that the problems of high volume expansion, low conductivity and slow ion diffusivity of silicon are solved.

The preparation method comprises the following steps: 1, dispersing an iron source, a phosphorus source, a lithium source, a carbon source, a dispersing agent, an element doping agent and a solvent in proportion, dividing the dispersed slurry into three parts of slurry A, B and C in proportion, respectively grinding the three parts of slurry, and respectively carrying out spray drying; 2, pre-sintering the three parts of spray materials at different temperatures, and crushing the pre-sintered materials; and step 3, mixing the crushed pre-sintered materials so as to realize multi-stage grain composition. Carrying out dry mixing on a carbon source and the pre-crushed material according to a certain mass ratio; and 4, carrying out secondary sintering, crushing and demagnetizing on the mixed material to obtain the multi-stage grading high-compaction lithium iron phosphate positive electrode material. According to the invention, primary sintering material grain grading and secondary carbon coating and sintering strengthening are realized through graded particle size design, and the compaction density and the specific capacity of the lithium iron phosphate positive electrode material are synergistically improved.

The invention belongs to the field of silicon-carbon negative electrode material manufacturing, and particularly relates to a preparation method of a vapor deposition silicon-carbon material based on supercritical carrier gas. The method comprises the following steps: carrying out vacuum degassing on a porous carbon material in a heating state, then taking supercritical gas as carrier gas, assisting with ultrasonic vibration, introducing silicon-containing gas to carry out silicon deposition, and repeatedly carrying out operation until the required silicon content is reached; and finally, introducing a carbon source gas for carbon coating to obtain the silicon-carbon composite material with the core-shell structure. According to the preparation method, uniform deposition of silicon in a porous carbon skeleton is realized through silane vapor deposition with supercritical fluid as carrier gas under the assistance of ultrasonic vibration, the first coulombic efficiency is improved, stress concentration and volume expansion in the charging and discharging process are reduced, and the cycling stability is improved.

The invention belongs to the technical field of lithium ion battery positive electrode materials, and provides a double-layer coated lithium iron manganese phosphate positive electrode material, which comprises a lithium iron manganese phosphate positive electrode material, and an organic carbon source coating layer and a modified carbon nanotube coating layer which coat the surface of the lithium iron manganese phosphate positive electrode material from inside to outside. Firstly, an organic carbon source is adopted to perform primary carbon coating on lithium manganese iron phosphate to form a carbon core-shell composite structure, and then modified carbon nanotubes are utilized to perform secondary coating to obtain the double-layer coated lithium manganese iron phosphate positive electrode material, so that organic-inorganic dual coating is realized, the electronic conductivity of the material can be effectively improved, and the performance of the material is improved. And the condition that the lithium manganese iron phosphate is directly contacted with the electrolyte to reduce the dissolution of Mn can be avoided, so that the cycle performance of the positive electrode material is improved, and the preparation process is simple in process, easy to operate and suitable for large-scale production.

A kind of preparation method of high compaction lithium iron phosphate of multistage gradation, including step one: iron source, phosphorus source, lithium source, carbon source, dispersing agent, element dopant and solvent are dispersed according to proportion, slurry after dispersion is divided into A, B, C three slurry according to proportion, three slurry are grinded respectively, and then are respectively carried out spray drying;Step two: three spray materials are respectively pre-sintered at different temperatures, and pre-sintered material is respectively crushed;Step three: the material after pre-sintering is mixed to realize multistage particle gradation.Certain mass ratio of carbon source and pre-crushed material are dry mixed;Step four: after secondary sintering, crushing and magnetic removal process, the multistage gradation high compaction lithium iron phosphate positive material is obtained.The present application realizes particle gradation of once sintered material, secondary carbon coating and sintering strengthening by grading particle size design, and realizes the collaborative improvement of compaction density and specific capacity of lithium iron phosphate positive material.

The invention relates to the technical field of lithium ion battery negative electrode materials, and discloses a preparation method and application of a high-efficiency silicon-carbon composite graphite material, and the preparation method comprises the following steps: S1, carrying out porosity and size regulation and control on silicon particles: carrying out ball milling on industrial-grade silicon powder to obtain nano silicon particles, and carrying out acid etching to form a porous structure; s2, functional surface treatment and interface optimization: introducing functional molecules to the surfaces of the silicon particles and coating a layer of ultrathin SiO2 protective film; and S3, carbon coating and flexible protection layer construction: performing pyrolysis on the porous silicon particles by using a carbon source to form a uniform carbon coating layer which is applied to a lithium ion battery negative electrode material, and the lithium ion battery is used for an electric vehicle, a power grid energy storage system and portable electronic equipment. Through the collaborative design of the flexible protection layer, the double-layer carbon coating and the gradient coating, the technical bottlenecks of the silicon-based negative electrode material in the aspects of long cycle stability, high rate performance and interface chemical stability are systematically solved.

The invention relates to a positive electrode material and a preparation method thereof, a positive electrode plate, a battery and an electric device. The positive electrode material comprises a positive electrode base material, a carbon coating layer and an aluminum fluoride coating layer, the positive electrode base material is coated with the carbon coating layer, and the carbon coating layer is coated with the aluminum fluoride coating layer; wherein the positive electrode base material is selected from lithium manganate; wherein the aluminum fluoride coating layer is a discontinuous coating layer. The positive electrode material has excellent high-temperature cycle performance and also has excellent rate capability and capacity.

The invention provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises a carbon-coated lithium iron phosphate material. By regulating and controlling the relative proportion of the specific surface areas of carbon structures with different micromorphologies in the surface layer of the carbon-coated lithium iron phosphate material, specifically, the carbon-coated lithium iron phosphate material disclosed by the invention has a carbon coating factor eta, and when eta is more than or equal to 0.81 and less than or equal to 0.95, the lithium iron phosphate material has high-quality carbon coating; the lithium iron phosphate material capacity exertion is facilitated, the pole piece dehydration efficiency is remarkably improved, and the prepared battery monomer has excellent energy density, cycle performance and processing performance.

The invention relates to the technical field of sodium-ion batteries, in particular to a sodium-ion battery positive electrode material and a preparation method thereof.The sodium-ion battery positive electrode material comprises a sodium ferric sulfate precursor and a carbon coating layer coating the surface of the sodium ferric sulfate precursor; the sodium ferric sulfate precursor comprises a sodium source, an iron source, an antioxidant and halogenated carboxylic acid; and the carbon coating layer is formed by coating and sintering phosphate. Aiming at the problem that a carbon-coated positive electrode material in the prior art is easy to form defect points, the carbonization temperature in the sintering process is reduced by adding halogenated carboxylic acid into a precursor, so that the carbonization effect is improved, the probability of forming the defect points is reduced, and halogen ions are introduced into a carbon-coated layer in the sintering process to improve the conductivity; meanwhile, surface coating is carried out through phosphate, so that reaction of the positive electrode and electrolyte under a high-voltage condition can be effectively inhibited, gradual deterioration of the material structure due to moisture absorption in the circulation process is avoided, and the circulation stability of the material is improved.

The invention relates to the technical field of lithium ion batteries, in particular to a silicon-carbon negative electrode material and a preparation method thereof. The preparation method of the silicon-carbon negative electrode material comprises the following steps: carrying out liquid-phase coating treatment on a porous carbon material and a fast ion conductor precursor to form a porous carbon material coated with a fast ion conductor so as to prepare a modified porous carbon material; carrying out first chemical vapor deposition treatment by taking silane gas as a deposition precursor, and depositing nano silicon on the surface of the modified porous carbon material to prepare a silicon-carbon core; and carrying out secondary chemical vapor deposition treatment by taking a soft carbon gas source as a deposition precursor in an inert gas atmosphere, and depositing nano soft carbon on the surface of the silicon-carbon inner core to prepare the silicon-carbon negative electrode material. The preparation method of the silicon-carbon negative electrode material solves the technical problem that the electrochemical performance of the silicon-carbon material is poor due to the fact that the volume of the existing silicon material is expanded and the ionic conduction performance is reduced by a carbon coating technology.

The present invention belongs to the technical field of battery materials, and particularly relates to a composite phosphate-based positive electrode material, and a preparation method therefor and the use thereof. The composite phosphate-based positive electrode material comprises a phosphate-based active core, wherein the outer surface of the phosphate-based active core is sequentially coated with a carbon coating layer, a nitrogen-doped carbon coating layer and a nitrogen-phosphorus co-doped carbon coating layer from inside to outside, wherein the carbon coating layer can improve the electronic and ionic conductivity of the composite positive electrode material, and optimize the particle size and morphology of the composite positive electrode material. The nitrogen-doped carbon coating layer improves the consistency and integrity of coating; and nitrogen-atom-doped carbon further enhances the electronic conductivity and lithium-ion diffusion of the carbon coating layer. Electron-rich clouds of P and N atoms in the nitrogen-phosphorus co-doped carbon coating layer can provide a rich conductive network, mutual contact is formed among different particles to form a series network, thus promoting the interfacial electron transport of the composite material during a charging and discharging process, and improving the cycling and rate performance of the composite phosphate-based positive electrode material during the charging and discharging process.

The invention relates to a spherical hydrotalcite phase desulfurization adsorbent as well as a preparation method and application thereof, the preparation method comprises the following steps: mixing an iron source, a nickel source and organic carboxylate, and then carrying out hydrothermal carbonization reaction to obtain the spherical hydrotalcite phase desulfurization adsorbent. The nickel source and the iron source are selected as the raw materials, hydroxide radicals of laminates and carbonate ions between the laminates of the prepared hydrotalcite phase desulfurization adsorbent can increase the alkalinity of the surface of the desulfurization adsorbent and improve the adsorption capacity to hydrogen sulfide, and meanwhile, the hydrotalcite phase desulfurization adsorbent can react with hydrogen sulfide in a catalytic oxidation manner, so that the removal efficiency is improved. Organic carboxylate is selected as a hydrothermal auxiliary agent, carboxylate radicals can chelate metal ions through multidentate coordination to form a stable complex, so that the nucleation rate of hydrotalcite is delayed, the particle size uniformity is improved, meanwhile, a carbon coating layer is generated through hydrothermal carbonization, and pores in the carbon coating layer and pores in hydrotalcite can form hierarchical pore channels, so that the composite material is prepared. The mass transfer efficiency is synergistically improved, so that the adsorption capacity of the adsorbent is improved.

The invention relates to a positive electrode material, a preparation method thereof and a secondary battery, the positive electrode material comprises a phosphate core and a carbon coating layer, the phosphate core is coated by the carbon coating layer, the particle size of primary particles of the positive electrode material is 250-450 nm, and the particle size variance of the positive electrode material is 1-10. The particle granularity of the positive electrode material is in normal distribution, the finished product particles are relatively large and uniform in size, and the compaction density and the capacity are remarkably improved; moreover, the surface of the phosphate core is uniformly coated with the carbon coating layer, and the thickness of the carbon coating layer is moderate, so that not only can the electronic conductivity of the positive electrode material be improved, but also the discharge capacity, coulombic efficiency and other electrochemical properties of the composite phosphate positive electrode material can be improved.

The invention discloses a preparation method of a carbon-coated single-crystal sodium ferric pyrophosphate positive electrode material, which is specifically implemented according to the following steps: step 1, dissolving sodium salt, ferric salt and phosphate in deionized water in proportion, then adding a carbon source into the solution, and uniformly stirring to obtain a mixed solution; step 2, fully drying the mixed solution obtained in the step 1 to obtain precursor powder; and 3, carrying out heat treatment on the precursor powder in a protective atmosphere, and cooling to obtain the carbon-coated single-crystal sodium ferric pyrophosphate positive electrode material. The invention also discloses a coating prepared by the method, a single-crystal structure is combined with uniform carbon coating, grain boundary defects are eliminated, conductivity is improved, high specific capacity and long cycle life are realized, single-crystal growth and carbon layer in-situ coating are synchronously realized by a synthesis process, and structural integrity and efficient conductive network construction can be ensured.